1. Field of the Invention
The present invention relates to a testing apparatus and a testing method for testing a device-under-test such as a semiconductor circuit. More specifically, the invention relates to a testing apparatus and a testing method for judging whether or not the device-under-test is defect-free based on its static power-supply current.
2. Related Art
Conventionally, there has been known a method of detecting an abnormal value of power-supply current by measuring the power-supply current supplied to a device-under-test test such as a semiconductor circuit as a method for testing the device-under-test. For example, it is judged whether or not a device-under-test is defect-free by applying various test patterns to the device-under-test, by detecting power-supply current of the device-under-test when it is in various operation states and by judging whether or not the power-supply current falls within a predetermined range.
However, due to refinement of a device-under-test and increase of a number of CMOSs contained in the device-under-test of recent years, leak current in such device-under-test is increasing. The leak current fluctuates depending on variation per device-under-test, temperature change and others. Specifically, so-called sub-threshold leak current in COMS largely depends on temperature, so that it is difficult to stabilize such leak current. Therefore, the conventional power-supply current test has had problems that the power-supply current supplied to the device-under-test fluctuates due to the fluctuation of the leak current and that the device-under-test is judged to be defective even if it ought to be judged to be defect-free.